i-bash/builtins/let.def

This file is let.def, from which is created let.c.
It implements the builtin "let" in Bash.

Copyright (C) 1987-2009 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Bash is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Bash.  If not, see <http://www.gnu.org/licenses/>.

$BUILTIN let
$FUNCTION let_builtin
$PRODUCES let.c
$SHORT_DOC let arg [arg ...]
Evaluate arithmetic expressions.

Evaluate each ARG as an arithmetic expression.  Evaluation is done in
fixed-width integers with no check for overflow, though division by 0
is trapped and flagged as an error.  The following list of operators is
grouped into levels of equal-precedence operators.  The levels are listed
in order of decreasing precedence.

	id++, id--	variable post-increment, post-decrement
	++id, --id	variable pre-increment, pre-decrement
	-, +		unary minus, plus
	!, ~		logical and bitwise negation
	**		exponentiation
	*, /, %		multiplication, division, remainder
	+, -		addition, subtraction
	<<, >>		left and right bitwise shifts
	<=, >=, <, >	comparison
	==, !=		equality, inequality
	&		bitwise AND
	^		bitwise XOR
	|		bitwise OR
	&&		logical AND
	||		logical OR
	expr ? expr : expr
			conditional operator
	=, *=, /=, %=,
	+=, -=, <<=, >>=,
	&=, ^=, |=	assignment

Shell variables are allowed as operands.  The name of the variable
is replaced by its value (coerced to a fixed-width integer) within
an expression.  The variable need not have its integer attribute
turned on to be used in an expression.

Operators are evaluated in order of precedence.  Sub-expressions in
parentheses are evaluated first and may override the precedence
rules above.

Exit Status:
If the last ARG evaluates to 0, let returns 1; let returns 0 otherwise.
$END

#include <config.h>

#if defined (HAVE_UNISTD_H)
#  ifdef _MINIX
#    include <sys/types.h>
#  endif
#  include <unistd.h>
#endif

#include "../bashintl.h"

#include "../shell.h"
#include "common.h"

/* Arithmetic LET function. */
int
let_builtin (list)
     WORD_LIST *list;
{
  intmax_t ret;
  int expok;

  CHECK_HELPOPT (list);

  /* Skip over leading `--' argument. */
  if (list && list->word && ISOPTION (list->word->word, '-'))
    list = list->next;

  if (list == 0)
    {
      builtin_error (_("expression expected"));
      return (EXECUTION_FAILURE);
    }

  for (; list; list = list->next)
    {
      ret = evalexp (list->word->word, &expok);
      if (expok == 0)
	return (EXECUTION_FAILURE);
    }

  return ((ret == 0) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}

#ifdef INCLUDE_UNUSED
int
exp_builtin (list)
     WORD_LIST *list;
{
  char *exp;
  intmax_t ret;
  int expok;

  if (list == 0)
    {
      builtin_error (_("expression expected"));
      return (EXECUTION_FAILURE);
    }

  exp = string_list (list);
  ret = evalexp (exp, &expok);
  (void)free (exp);
  return (((ret == 0) || (expok == 0)) ? EXECUTION_FAILURE : EXECUTION_SUCCESS);
}
#endif